FIG. 1 depicts a conventional method 10 for providing a conventional magnetic element, such as magnetoresistive elements used in read transducers. FIGS. 2-3 depict the conventional magnetic element during fabrication. Referring to FIGS. 1-3, the layers for the conventional magnetic element are deposited, via step 12. For a conventional tunneling magnetoresistance (TMR) stack that may be used in a read transducer, step 12 may include depositing a pinning layer such as an antiferromagnetic (AFM) layer, a pinned layer, a nonmagnetic spacer layer, and a free layer. The pinned and free layers are typically ferromagnetic or synthetic antiferromagnetic layers including two ferromagnetic layers separated by a nonmagnetic, conductive layer. For a conventional TMR stack, the nonmagnetic spacer layer is an insulator, such as Al2O3, crystalline MgO, and/or titanium oxide, that provides a tunneling barrier.
A conventional undercut bilayer structure is provided on the conventional magnetic element layers, via step 14. FIG. 2 depicts the conventional magnetic element layers 20 and the conventional undercut bilayer structure 30. The conventional magnetic element layers 20 include an AFM layer 22, a pinned layer 24, an insulating, nonmagnetic spacer layer 26, and a free layer 28. Other layers, such as seed or capping layers, might also be used. The conventional undercut bilayer structure 30 includes two layers 32 and 34. The lower layer is typically a PMGI layer 32, while the upper layer is typically a photoresist layer 34. The PMGI layer 32 is narrower than the photoresist layer 34 to provide the undercut 36.
The pattern provided by the conventional undercut bilayer structure 30 is transferred to the underlying magnetic element layers 20, via step 16. In step 16, therefore, the magnetic element is defined. FIG. 3 depicts the conventional magnetic element 20′ that has been formed prior to removal of the conventional undercut bilayer structure 30. The conventional magnetic element 20′ has been defined from the layers 22′, 24′, 26′, and 28′.
Processing is completed for the conventional magnetic element 20′ and the conventional device in which the conventional magnetic element 20′ resides, via step 18. Step 18 includes lifting off the conventional undercut bilayer structure 30, which exposes the underlying conventional magnetic element 20′. Step 18 may also include providing subsequent layers and processing steps. For example, insulating layers, hard bias layers, fillers, and contacts to the conventional magnetic element 20′ may be provided in step 18. Typically, these layers are provided prior to lift-off of the conventional undercut bi-layer structure 30 so that the conventional undercut bi-layer structure 30 can act as a mask for the conventional magnetic element 20′. Thus, the conventional magnetic element 20′ in a conventional device, such as a read transducer and/or merged head, may be formed.
Although the conventional method 10 and the conventional magnetic element 20′ can function, one of ordinary skill in the art will readily recognize that the trend in magnetic recording technology is toward higher densities and smaller sizes. Thus, the critical dimensions in write or read heads are currently below those in semiconductor processing. Further, as sizes shrink to provide areal densities above 120 Gb/in2, the lift-off performed in step 18 becomes more difficult. For printed critical dimensions of the photoresist layer 34 below 0.1 micrometer, it is difficult to provide a small enough the PMGI layer 32 to generate a sufficient undercut for lift-off. For example, the undercut 36 must typically be greater than at least 0.03 micrometer for complete liftoff of the conventional undercut bilayer structure 30. This means that the PMGI layer 32 is only 0.04 micrometers in width for a 0.1 micrometer photoresist layer 34. For smaller geometries having critical dimensions of less than 0.1 micrometer, the PMGI layer 32 may become too thin to support the photoresist layer 34, causing the conventional undercut bilayer structure 30 to collapse. Thus, transfer of the pattern of the conventional undercut bilayer structure 30 to the conventional magnetic element 20′ and liftoff of the conventional undercut bilayer structure 30 become difficult. For areal densities of 200 Gb/in2 and track widths of 0.08 micrometer or less, the conventional method 10 and conventional undercut bilayer structure 30 may be incapable of fabricating the conventional magnetic element 20′.
Accordingly, what is needed is a system and method for providing a magnetic element having smaller critical dimensions.